California has effectively become a one-party state. Election Day 2012 earned Democrats a two-thirds majority in both houses of the state legislature, the first time in 80 years that any party has achieved that feat in California. That will allow them to pass virtually anything they want in the next legislative session, including crafting ballot initiatives or passing laws to raise taxes that have previously been opposed by Republicans. But the GOP’s newfound insignificance in this state legislature isn’t its greatest worry. Republicans are warning that if the national party doesn’t heed the example of California, it could head toward political irrelevance on a larger scale.

That’s because it was the California GOP’s alienation of minority — especially Latino — voters starting decades ago that planted the seeds for its losses this month. Indeed, an important factor in Mitt Romney’s defeat was lopsided Latino support for President Obama. “California Republicans are becoming the white man’s party,” says Allan Hoffenblum, a former manager of local GOP campaigns in California who now publishes the California Target Book, an almanac on the state’s election campaigns. “Now I see the same thing happening on the national level. If the Republican Party doesn’t reform itself and become a viable party again, something else is going to replace it.”

There was a time when California was Republican. The state voted red in six straight presidential elections until Bill Clinton’s victory in 1992. Since then, it has voted solidly Democrat for President. Experts say this decline can be partly traced back to former Republican governor Pete Wilson’s endorsement of Proposition 187, a 1994 ballot initiative that aimed to deny undocumented immigrants access to public services. “Prop 187 really inflamed the very nasty polarizing debate over immigration and the hard rhetoric of the conservative right,” says Sherry Bebitch Jeffe, senior fellow at the USC school of policy, planning and development. The measure passed, but a federal court ultimately found it unconstitutional. More important, the state’s Hispanics found the proposition appalling and rallied their communities to reject it and the party that endorsed it.

“These people were angry,” says Arturo Vargas, who at the time worked at the Mexican American Legal Defense and Educational Fund. Since then, the GOP’s attitude toward Latinos hasn’t softened, and Hispanics’ allegiance to Democrats hasn’t either. Meanwhile, the Latino population ballooned with an influx of immigrants, only adding to the ranks of Democratic voters. Over time, districts that were traditionally red turned blue, and there were more areas where GOP candidates couldn’t be competitive. “History has shown that that moment galvanized Latino immigrants,” says Vargas, who is now executive director of the National Association of Latino Elected and Appointed Officials. “That’s why California is so blue today.”

Blue is an understatement. Not only did Democrats win a supermajority but Obama and the state’s Democratic candidate for U.S. Senate both got landslide victories, voters approved a key tax increase opposed by Republicans, and GOP voter registration dipped below 30%, which is not much greater than the percentage of voters with no party preference. Governor Jerry Brown too is a Democrat and could be re-elected if he decides to run again in two years.

California Republican Party Chairman Tom Del Beccaro recognizes the state’s changing demographics are a factor in these losses. While much more measured in his comments, even Del Beccaro says the GOP’s inability to effectively engage minority voters in the state is a “warning.” “Republicans haven’t developed a relationship with Latino voters throughout the state,” he says in an interview. “They haven’t been aggressive enough talking to Asian voters, Latino voters, black voters and young voters.”

Del Beccaro, though, doesn’t believe it’s the end of the road for California’s Republican Party. Democrats’ current policies as well as new legislation they may pass with their supermajority — such as tax increases and heavy regulations on business — could make the economy worse in two years than it is now, which would prompt more voter discontent with Democrats, he says. “Republicans need to start working today, going into the districts, explaining that those policies are hurting jobs and developing relationships with voters so that two to four years from now, voters will consider them as an alternative to Democrats,” he says. In an editorial on Monday, the Los Angeles Times urged Democrats not to “go crazy” with new tax legislation. “Democrats, please. Slow down. Exercise some restraint,” the editorial read. “Please don’t crash, lest you take California down with you.”

Still, Republicans in other parts of the country are seeing California as a potential bad omen. Jorge Luis Lopez, a Miami Republican who has led fundraising efforts for multiple campaigns and volunteered at the grassroots level for Romney, said Republicans are “doomed” in Florida and on the national level if they follow the path of the harsh rhetoric that hurt California’s GOP. In fact, a poll by Miami’s Bendixen & Amandi International showed Obama nearly pulled off majority support from Cuban Americans, whose support for the GOP used to be a given. “If Republicans want to engage the Latino community, we have to be able to get past the initial question of how compassionately we’re going to address the immigration issue in America,” Lopez says.

Indeed, the big question is whether Republicans are willing to work with Democrats to achieve comprehensive immigration reform. While recent overtures by House Speaker John Boehner suggest his party may be ready to do so, pure legislation may not be enough. Years of harsh rhetoric — made worse by Romney’s calls for self-deportation during the primaries — has led some Latinos to think the GOP regards them as inferior, says Dan Schnur, director of the Jesse M. Unruh Institute of Politics at USC. And that needs to be mended if the GOP is to right the ship. As Schnur says, “A Latino business owner isn’t going to want to hear what a candidate has to say about the capital gains tax until he’s convinced that politician doesn’t consider him and his family to be something less than human.”